Kablam !! Big bang. Cracked valve cover - Page 3 - PeachParts Mercedes-Benz Forum

#31 06-16-2002, 02:33 AM

This is the front tower that really got mangled.
The bolt protruding out the back held one of the chain guides as I recall. Oops, I better check that before reassembly.

#32 06-16-2002, 02:34 AM

Sorry, that'll have to wait until later.
I didn't think to take a picture of that.

JimSmith · #33 06-16-2002, 02:39 AM

Anon-E-Mouse,

Nothing like a visual presentation to make the point. Great photos. Looks like the damage was at the #4 or #5 cylinder, and those pistons looked pretty good. So maybe some engineer from the Fatherland really designed the top end to fail and protect the lower end! The thoroughness of the engineering on these machines just never ceases to amaze me.

If you are interested I can scan some images from the manual to show you how the chain path is set up, and how you might get that old chain out. Seems like an odd failure, as I though your engine was actually relatively recently "refreshed" and that usually includes a new chain. How is the vacuum pump? These can be the original failure point, as when they go, parts can fall into the chain path and snap the chain and other pieces in the path.

Good luck and glad you seem to be getting into the tear down and refurbishment. Jim

#34 06-16-2002, 03:03 AM

You're glad I'm getting into the tear down and refurbishment ?

Yikes !
Oh well, in for a penny, in for a pound.
Vacuum was working just great prior to, so I'm ruling that out for now although I could be surprised.
"relatively recently "refreshed"" ?
Not as far as I know. I adjusted the valves a couple of weeks ago but I have no prior history on the car. As is, where is from a small time dealer and no documentation or anything.
Yeah I know there's a lesson here but it was damn cheap and I thought I'd take a chance. I may still get out of it OK.

Scanned images sounds great.
I still haven't acquired any MB manuals and the trusty Haynes . . . well . . I've already *****ed once on another thread so no need to continue on that one.
I'm starting to think I can do the job myself. It'll be time consuming but there's a nice logic to everything MB does and except for their fan belt silliness which I've pretty much conquered now I anticipate success. What's scaring me now is all the timing business I've been reading about. Ignition timing, pump timing etc.
It all makes me a bit nervous.
I have to leave El Computadore now for someone's 40th an hours drive away so I'll get back to this tomorrow. Thanks for all the assistance.

Jim

engatwork · #35 06-16-2002, 07:37 AM

probably one of the easiest things to do. Put the engine at 24 degrees before TDC and line the injection pump marks up, install it on the block and tighten it down.

You should be able to use a magnet to pull the chain up and turn the engine. I'd suggest pulling it out and going through the lower end. You will want to establish a good relationship with a local machine shop - preferably one that does diesel engines. If you do all the work yourself you should be able to fix what you have with under US$1000. Tour the local "pull a parts" places and see what you can find. I saw a 300D cylinder head at the one I go to this past Friday.

The problem arises when you pull the pistons out and see the wear. If you are like me you will want to go ahead and make everything "new". The pistons are the most expensive part in that engine and if you have to purchase new ones you can plan on spending another US$600 or close to it.

I say go get the engine lift. You will enjoy it.

The bad thing about these unplanned rebuilds is that you don't have time to clean the engine up. That is why my engines are always clean.

JimSmith · #36 06-16-2002, 09:56 AM

Jim,

Well, it is better you are approaching the challenge with the frame of mind you seem to have than if you were just miserable about the whole thing. Obviously no one enjoys costly and time consuming repairs, and I would not wish them on anyone, but if you have to do it, well, like you said "in for a penny, in for a pound."

I must have your car confused with another member of this board. I thought it was one that had been quasi-rebuilt by the previous owner. Now you are making me nervous about the 1982 240D my daughter uses. It has over 280k miles and has the original chain. But it has had reasonable oil changes using synthetic oil since we have owned it, which happened when it had 105k miles. I check the vacuum pump for noises periodically and it has yet to change.

What kind of manual information are you looking for? I will get busy today and scan a view of the chain path and try to post it. If you want, send me an email and I will send the images in larger format to you via return email. The 65Kb limit and 600x800 size restrictions make the scanned image detail less than really clear. Text and the like can be difficult to read.

Good luck, Jim

tcane · #37 06-16-2002, 12:54 PM

Anon:

A quick reply because I have to be someplace soon.

Great pics. Looks like #3 intake valve has a big nick in it - is this so (did something enter the engine and cause the chain to break because the foreign item got between #3 intake valve and the piston locking the engine up for a moment?!?)? #3 and #4 ex. valves look bent, other valves I can't tell if they are bent. You'll need to remove all valves (keeping them sorted, cardboard marked with what went where works for me - or your own method) and roll them on a very flat surface to see if the head wobbles. If the valve head wobbles, then replace (you really need a dial gauge to see how much wobble there is because a very, very small amount of wobble can be corrected by the machine shop when refacing the valves: wobble = run-out).

The chain tensioner is broken at the lower end and the missing part needs to be found (probably in oil pan).

Folks keep talking about a design feature that the cam bearing/tower are meant to break when something like this happens. I have never seen any info/reference to this design feature and my experience is that most engines are not designed with such a feature because of the chance the break away part will break away when it is not suppossed to. Anyone have info on where to find a reference to this design feature? If so, I would appreciate it very much. Besides, if the cam bearing/tower are meant to break away so other damage does not occur - then why is the cam broken in two pieces? Just a thought.

The timing chain may have caused more damage than what is apparent given it broke the lower end off the chain tensioner. You will probably need to turn the engine opposite to engine rotation to free the chain (engine normally turns clock-wise looking at the engine from the front). Putting the balance plate (harmonic balancer) is a real PIA job if you have never done it before (the pins are a PIA to line up) so remove the plate on the trans where the bolt are that connect the flywheel to the torque convertor - then turn the flywheel to try and free the chain so you can pull it up. If you need to put the balancer plate back on to turn the engine, then look for an old post be me on how to do this job without damaging the crank and/or balancer plate (if this is not done right, then damage will occur).

Given the nature of the failure, I suspect the timing chain gear on the crank is damaged (perhaps broken teeth). This gear needs to be removed for close inspection. This can be hard to remove with the engine in the car without the M-B special puller that is small and just fits into the opening leading to the gear and just fits over the gear to remove. You might get lucky and your gear (along with the crankshaft spacer ring the front oil seal rides on) will slide off the crank easily - but, probably have to find the high spots on the crank to sand down so the gear and spacer will slide out (I mean sand only the high spots with progressively finer grit sand paper - 100-220-400-600 - and not the entire front section of the crank, I've done this on two cranks).

To access the timing chain area from the bottom, the lower and upper oil pans have to be removed. Lower (small) oil pan R&R is nothing labor-wise. The upper oil pan can be removed with the engine in the car, but you have to disconnect lots of stuf so you can use a hoist to raise the entire engine high enough to remove it (almost everything is removed as in getting ready to remove the engine completely from the body).

Your mechanic friend is skeptical about the bottom end even without much apparent damage to the pistons - based on his experience and seeing too many times when there appears to be no damage, when in fact there is damage. I have the same opinion considering the pics. But, as you said "You feel lucky." If so, then I'd also buy some lottery tickets!

! (this is only a joke and meant to lighten the mood a bit considering the problem Jim has to deal with).

Engatawork is right about timing the crank to cam to injection pump - it is straight forward once you read and understand the relationship. Then precisely timing the injection pump by doing the start of delivery is the trick (think using a timing light to adjust the ignition timing on a gas engine). TXBill, leathermang, and I did a start of delivery on leathermang's 240 last weekend taking pics for the DIY section. I need to do to do the write-up and then you will see how the procedure goes.

The timing chain on these engines should last as long as the rest of the engine with regular oil/filter changes at 3,000 miles or so (using dino oil) and using a good diesel rated oil. This leads me to believe that either a foreign object entered the engine shown by the nick in #3 intake valve (if that is what it is from the pic) or oil/filter changes were not done regularly and/or the oil was not good causing more grit than usual to enter the timing chain rollers acting like sandpaper to prematurely wear out the chain. If the oil/filter was not changed regularly, then the rest of the engine may be worn or close to max spec and a complete TDI needed to inspect perhaps leading to a complete rebuild. Or, find another engine if parts/labor costs on your engine increase beyond economic reality.

My, very cheap, $0.02 Worth!
Tom

P.E.Haiges · #38 06-16-2002, 01:31 PM

You don't have to remove the engine to check the timing chain sprocket. It can be viewed by taking off the front balancer and that is a lot easier than R&R the engine. Removing the balancer will also male it easier to install the new chain. The front oil seal must be removed to be able to see the sprocket and that will damage the seal so it will have to be replaced. Job will be easier if radiator is removed first.

Check all the chain guides and replace any that are damaged.

Its a 27mm socket that fits on the crankshaft nut not a 19 mm. If you don't have one, get a 27mm deep socket and it can also be used to remove the injectors. Hint: a 1 1/16 inch socket will also work.

To break a chain it seems that something must have gotten into the moving chain to cause it to break so check for any other loose parts in there, especially the vacuum pump.

Timing the injection pump (IP) is probably the most difficult part of the job. You have to remove the pump, time the cam to the crank and the set the timing marks to a certain number of degrees from TDC and reinstall the IP having set it to a certain angle. These angle values can be found in an engine repair manual. This gives you the rough setting and then the drip tube method must be done.

P E H

#39 06-17-2002, 02:01 AM

Took a picture for those interested in the valve cover.

#40 06-17-2002, 02:06 AM

Tom : here's another picture of the valves. The first picture made it look like a nick but as you can see here they seem to be in good shape.

#41 06-17-2002, 02:07 AM

more detailed picture.

#42 06-17-2002, 02:45 AM

Unbelievable help from you guys.
I hope I can make use of all this advice 'cause I'd hate to have to report a failure on this job. I'm starting to feel like I owe it to everyone to finish the job as your involvement deserves it.
That sounded confused but I hope you get what I'm trying to say.

Anyways, I guess that means a bit of an apology for not having more to report.
I removed the radiator today and the power steering bracket. I filled the cylinders with some ATF I had hanging around to see if it would seep past the rings. It didn't.
I got hung up on removing the water pump pulley, another simple job where the devil's in the details. I have two bolts there that are not coming out and I starting to strip their heads. I now need a 9 1/2 mm wrench or something like that

Maybe I'll just torch them off and extract the rest later.

engatwork,

Setting the injection timing is sounding easier than before. I guess I can manage it.
Pulling the chain up with a magnet is not going to happen. It's completely jammed up on itself.
I'm almost ready to pull the oil pan but today got the better of me and it'll have to wait.

Tom,

As for the cam tower's being designed to break; I'd guess it's not so much a brilliant design feature as just a happy design coincidence that others have noticed.
Despite your confidence in me I thought I'd get the machine shop to do all the valve work for me. It will depend upon the cost of course but I'd feel better knowing somebody with more experience was doing the work.
As for your very cheap two cents worth . . I know they say that advice is worth what you pay for it but in this case I disagree.

Jim,

You're a great help and you're keeping me optimistic which now that I've gone further and had more time to reflect on the task, is becoming more difficult. I would like to see a couple of drawings from the manual but I'm not at the point yet where I'm even sure what I need. I will email you soon though and thanks.

P.E.Haiges,

I bought a 1 1/16 deep today (1/2" drive) and used a 3/4" to 1/2" adapter for extra depth and to be able to use my 3/4" drive ratchet. I couldn't turn the engine clockwise 'cause I guess the chain is binding and when I tried to turn it the other way it just started undoing the nut.
Also, isn't removing the balancer kind of a big deal because it has to be put back on a certain way ?

I am not sure how fast I will be progressing on this over the next few days as work will be occupying my time quite a bit this week but I'm hoping to get the head into the shop tomorrow and should have some news on that soon.

once again, thanks to all.

jim.

P.E.Haiges · #43 06-17-2002, 09:28 AM

Balancer is no problem to reinstall. Its been a long time since I did mine to replace the front seal but I seem remember it is aligned by 2 dowel pins and somehow keyed to the crankshaft and can only be put on one way. It has to be aligned to the crank because besides being a balancer, it is used to time the crankshaft to the cam and injection pump.

To replace the front oil seal (OS) you should buy a second ring that the OS rides on. The lip of the oil seal goes toward the rear of the car and you can't slide the OS onto the ring. So you put the OS on the second ring, slide the second ring on the crankshaft and then push the OS in place and remove the second ring.

I wouldn't R&R the oil pan except as a last resort. Its a lot of work and might not be of any help. I remember I replaced a broken chain without R&R the oil pan. Try fishing with a coat hanger with a hook formed on the end to get out the old chain. Its the chain jamming in the sprocket that is keeping the engine from turning.

Good luck.

P E H

tcane · #44 06-17-2002, 01:25 PM

Jim (Anon):

Your second set of pics is better for seeing the valves. The first set made it look like there was damage, not present in the second set. However, a bent valve may not be apparent until the valve is removed and inspected. The machine shop will be able to tell you what needs replacing. A word of caution, do not take the head and have it repaired (inspection with an estimate of repair cost is OK) until you have determined all the damage the engine may have. My concern is with the timing chain and what damage it may have caused to the crank, block, etc. which you have not inspected yet because you cannot free the chain. My suggestion to use the flywheel to turn the crank is one way to turn the crank and if that does not work then removing both oil pans to access the lower timing chain/crank gear/crank area in order to locate an area to place a pry bar to rotate the crank to free the chain is the other.

Actually, installing the balancer plate (M-B term and not harmonic balancer which is wrong terminology) is very hard to do, unlike what has been stated and, in my opinion, is harder to do than timing the crank to cam to injection pump. The balancer plate (BP) can be put on 180 degrees out of position if the the #1 piston is not at TDC and the 0 degree mark on the BP is not lined up with the pointer mounted on the engine block. The two pins that locate/index the BP to the crank are not like a single woodruff key that would prevent the BP from being mounted incorrectly. Installing the BP is especially hard with the engine in the vehicle because the AC condensor prevents a direct on end view of the BP and crank, instead you have to use a mirror and light to view the BP and crank, and then deal with the fact that what you see in the mirror has to be reversed when moving the BP to line up the notches where the pins are installed. Even if you remove the AC condensor or your car does not have AC, installing the BP is difficult. Making the installation difficult is the fact that the notch cut-out on the BP is not machined all the way through and the BP has to be mounted about half-way onto the crank before you can do the fine movement of the BP to get a perfect alignment of the notch cut-out in both the BP and crank (initially, only a rough alignment of the pin notches can be done because the notch cut-outs on the BP are mahined from the front of the BP and and extend only half-way through the BP, when the BP is a bit over half-way on then the notch alignment can be seen and then the BP moved to get a perfect alignment before moving the BP to close to the fully installed position on the crank and then installing the pins - neither M-B or Haynes or any other manual cover this installation as well as it should be) . Anything less than a near perfect alignment will result in damage to either the BP or the crank and maybe both. Do a search on the forum and you will find several about ruining the BP and/or the crank by doing the installation wrong. Look for one of the two posts by me on the correct way to install the BP to the crank perfectly so neither is damaged and perfect alignment is achieved as verified by use of a dial gauge.

The suggestion on how to Install the front crank oil seal is also incorrect. The crank spacer can be installed either on the crank before installing the oil seal or the spacer placed inside the oil seal and then both installed at the same time (I've installed several oil seals with the crank spacer mounted on the crank without problems). In either method the crank must be smoothed with sandpaper (as I wrote before) so the crank spacer and timing chain sprocket gear slide without binding (this also helps with installing the BP). Using a second crank spacer is unneccessary and a waste of money if the original crank spacer is in good condition (as they usually are because they are hard chromed unlike the earlier crank spacers). The crank oil seal can either be tapped into positon with a soft faced hammer or better use a ring of some sort (large socket, etc. I have special rings for mounting oil seals) to place over the oil seal to help move the seal evenly as it moves into the block. With a coating of oil on the oil seal lips (2 an inner and outer) and on the outside the installation goes easier and removes the chance of damaging the seal when the eengine starts because the oil seal's lip is lubed.

The issue of removing the timing chain is one reason why I provided info on how to remove the oil pans. Since the chain is jammed around the timing gear/crank removing the oil pans may be the only way to free up the chain. Another reason to remove the oil pans is to get a good view of the timing gear on the crank to inspect for damage (since it is a double row chain any inspection through the front crank oil seal area is obstructed, incomplete, and will miss damage on the back row of teeth), if you cannot get the special tool to remove the gear from the crank then you may be able to pry on the gear/crank to remove the gear and the only way to do this is to remove the oil pans.

Another important reason to remove the oil pans is to find debris from the broken parts and since it looks like the timing chain guide on the front cam bearing mount is missing it may be in the upper oil pan lodged in such a way that it will not move into the lower pan since it is made of plastic and not as heavy untill oil starts flowing over it - as well as other debris like the broken off end of the chain tensioner. The last thing you want is debris floating around that could/will clog the oil pump pick-up screen and reduce/stop oil flow causing the engine to seize. This info from Chevy and wet sumps (engine oil is in the oil pan versus a dry sump where the oil is pumped out into a separate tank): as engine RPM's increase the oil in a wet sump system is whipped by the turbulence created by the crank throws, this turbulance results in the oil being agitated, eventually some oil separates from the main oil pool and is suspended, oil escaping the crank and rod bearings join the suspended oil (this oil is the oil that lubricates the pistons and cylinder walls - in addition to the oil jets M-B had to install on the turbo 300D engines to cool the inside of the piston/small end of the rod), as RPM's increase further the amount of suspended oil increases and grows into a mass, with further RPM increases the suspended oil mass increases in size and the crankshaft slams into the suspended oil mass breaking the crank. This is one reason why most race engines have dry sump oil systems (another is additional cooling and filtering along with the ability to fill-up oil during a race). The importent point here is that the turbulance in the oil pan area is great enough to stir the oil up more than enough to pick-up debris that is then picked-up in the oil pump screen and can/will clog it stopping oil flow and damaging the engine. I've seen lots of oil screens that were clogged with debris damaging the engine and the importance of finding all debris and removing it is very important - even a diesel engine with a 5,000 RPM redline.

The differences expressed here are the result of a professional (me) with the associated education, training, and experience with many 1,000's of engine rebuilds done with success including 100's of racing engines.

Good Luck!
Tom

P.E.Haiges · #45 06-17-2002, 08:35 PM

I don't disagree with anything Tom says. I removed my BP about 5 years ago to replace the front oil seal and I don't remember it being much of a problem to reinstall. You have to install the BP in the same position with respect to the crankshaft that it was removed so punch marks are probably appropriate.

Since you have to remove the ring the oil seal seals on to remove the sprocket, you may be able to install the seal and the ring at the same time eliminating the need for the second ring as I explained.

Different strokes for different folks goes for mechanics too. Two mechanics may do the same job in different ways. As far as service manuals go, they are not always correct, even the MB ones. My MB service for my '74 190D said to remove the upper oil pan, the engine must be removed from the car. I found this wasn't true. Not only did I R&R the oil pan without removing the engine, I R&R the crankshaft too.

P E H